Preview only show first 10 pages with watermark. For full document please download

5. Hill Roads 073 Old.pptx




5. Hill Hill Roads Roads Topics As Per Syllabus 5.1 Introduction 5.2 Special Consideration Considerati on in Hill Roads 5.2.1 Alignment of Hill Road Design: General Consideration, Route ocation in Hills, Gradient, Design and !"pes of Hair #in $ends, Di%erent !"pes of Hill Road Cross§ions 5.3 Special Structures in Hill Roads 5.'.1 !"pes of Retaining Structures, Ri(er !raining 1. Introduction • A +ill road is usuall" dened on t+e )asis of terrain. • As per -RS t+e cross slope ma" )e classied as: • Road +ic+ passes t+roug+ it+ a cross slope of 25/ or more i.e. mountainous or steep is termed as 0Hill Road. • Hill road&one +ic+ passes t+roug+ terrain it+ cross slope of 25/ or more. • !+ere are sections along +ill road it+ cross slope less t+an 25/, esp. +en t+e road follos ri(er route. • It is t+e o(erall terrain t+at must )e considered. Why Hill Road in Nepal? • -epal area  134,444 s. 6m appro7. • 88/ co(ered it+ t+inl"9sparsel" populated +ills, mountains. • 4/ population reside in +ill" areas and depends on agro products. • ;atera"s, raila"s, aira"s & di7tremes of Climatic Conditions, Diconom", Social Reasons = ustif" t+e Construction of Hill Roads in t+e Hill" Regions. ;+ere !unnels, ?iaduct = #ossi)le )ut -ot >conomical 5. Special !onsideration in Hill Roads 5..1 "esi#n and !onstruction Proble$s o% Hill Roads • C+aracteri*ed )" a +ig+l" )ro6en relief it+ idel" di%ering ele(ations and steep slopes, deep gorges and se(eral atercourses E unnecessaril" increase in road lengt+ • Comple7 geolog" & di%erent roc6 )ed& geolog" di%ers from place to place = assessment for road foundation is not eas" • >n(ironmental impact & remo(al of (egetation etc. & sta)le slope ma" c+ange to unsta)le slope after road construction • Great ?ariation in +"drological condition Fground ater condition (ar" from place to place = ma" lead to damages after road construction • -e eart+ ll for road em)an6ment ma" o(erload t+e relati(el" ea6 underl"ing soil la"er on +ill slope = ma" trigger ne and recurrent slides • Reuires installation of (arious t"pes of special &arious road structures ' cost ma" rise upto 54 & 84/ of total construction • Steep slopes = +ig+ speed of surface runo% & pro(ision of erosion protection or6s • Construction along relati(el" small approac+ di%erent construction tec+nolog" ma" )e needed stretc+es= • -eed of special safet" precaution during construction • ?ariations of climatic conditions & precipitation Frain and sno , (elocit" of ind etc. & need considerations • @reuent )lasting • Design of +airpin )ends to get +eig+ts    ङ र मनङ समम पन मभरक कच बटम दनक उपभगय वत       प     यर !क"द यत  $व%क  #  लमज  जप%& ' यत() र   ,  ,नयवस र पय-टक .सरर%) क /न  #  मनङम *+ वट जपल) उपभगय वत  5.. Special !onsideration in Hill Roads 1. Selection of Road Alignment 2. Special Geometric Standards BGradient and Hari #in $ends '. Cross§ion Design 3. Design of Drainage Structures BSpecial Structures ma" Reuire 5. Sta)ilit" of Slopes 1. Selection o% Road Ali#n$ent • Alignment t+roug+ +ill" areas is slig+tl" di%erent from aligning t+roug+ a at terrain. • @or t+e purpose of e7cessi(e cutting and lling for road constructions gi(e a" to steepening of slopes +ic+ in turn ill a%ect t+e sta)ilit". *actors A+ectin# Selection o% Ali#n$ent in ,ountainous and Hilly Areas • @olloing points to )e considered +ile aligning t+e +ill roads: i- Te$perature •)  !+e temperature of air (aries in(ersel" it+ altitude. •)  !+e temperature drop )eing a)out 4.5 4C per 144m of rise. •) Similarl", t+e amount of +eat recei(ed )" +ill slopes (aries enormousl" it+ t+eir orientation in relation to t+e e7posure to sun. •)  !emperature & loer temperature in +ill = drop )" 4.5 4C per 144m rise & slopes facing sout+ and nort+ ii- Rain%all •)  !+e amount of rainfall in +ill" region is in(ersel" proportional to t+e altitude. •) In +ill" regions, ind often os along t+e (alle" and gorges, as conseuence of +ic+ t+e rainfall in t+e (alle" is su)stantiall" +ig+er t+an on +ig+&lands and ater&s+eds. •) Also, ma7imum rainfall occurs in fe mont+s onl". So t+ese all une(en situation create t+e pro)lem in construction and maintenance of t+e road. •) Rainfall& +ea(" rainfall a%ects construction and maintenance iii- At$ospheric pressure and Winds • Atmosp+eric pressure is in(ersel" proportional to altitude. • At +ig+ altitudes, t+e (elocit" of ind is freuentl" coming at 25 = '4 m9s. • !+e c+ange in c+aracter of ind is due to apprecia)le di%erence of atmosp+eric pressure in (alle"s and on mountain passes. • ;ind&+ig+ ind (elocit" contri)ute to damage =eat+ering of roc6s, )loing aa" )inding material in (alle" i&- (eolo#ical condition • !+e tendenc" of sedimentar" roc6s is to slip under t+e inuence of force parallel to t+e la"er. • !+e degree of sta)ilit" of +ill slopes depends upon t+e t"pe of roc6, t+e degree of strata inclination or dip, t+e occurrence of cla" seem, t+e +ardness of roc6 and presence of ground ater. • !+e insta)ilit" of road ma" )e due to ground ater, landslides and unsta)le folds. &- Route location •) !+e approac+ to t+e location of +ill road alignment (aries for t+e sections along t+e (alle" )ottom and along t+e mountain pass. •) !+e rst is called Kri(er routeL and second is called Kridge routeL. Route ocation • Hill road follo tist and turns& cur(es • ocation of alignment (aries for sections along (alle" and mountain pass • Alignment t+roug+ (alle" & ri(er routeM mountain & ridge route • A +ill road ma" )e onl" ri(er route, ridge route or com)ination of )ot+ Ri&er Route situated • Ser(es rural settlement ne7t to t+e ater course • o (e+icle operation cost Rid#e Route • Steep gradient, s+arp cur(es including +air pin )ends • • A(aila)ilit" of material and ater construction • >7pensi(e roc6 or6s, successi(e mountain pass Route clim)s up continuousl" from t+e (alle" till mountain pass and descends don • In(ol(es numerous +ori*ontal cur(es, construction of large • Construction of special structures, tunnels, sno fences etc. )ridges • Special retaining protection on +ill sides • Ri(er training or6s ma" e7tensi(e& toe cutting, etc. )e • Are most sta)le a- Ri&er Route • !+e location of a route along t+e ri(er (alle" is 6non as ri(er route. Ri(er route is freuentl" used in +ill road due to comparati(el" gentle gradient. - It is ad(antageous t+at a(aila)ilit" of ater and ot+er construction material in (icinit". - Hoe(er, a ri(er route ma" in(ol(e numerous +ori*ontal cur(es, construction of large )ridges o(er tri)utaries and on stretc+es along steepl" sloping +ill sides. & It ma" also )e necessar" to construct special structures on +ill side for t+e safe of road against landslides. b- Rid#e Route • A ridge route is c+aracteri*ed )" (er" steep gradient, numerous s+arp cur(es including +air pin )ends and t+e e7pensi(e roc6 or6s. & !+e road usuall" follos t+e top section of t+e +ill s"stem and crosses successi(el" mountain pass. & Geologicall" sta)le and comparati(el" mild slope sections are selected for t+e articial de(elopment of t+e route.